The present invention relates to a reference pulse generator for attaining low-power consumption.
In electronic timepieces, a pulse generator using a quartz resonator as a reference signal source has been used to minimize power consumption in a quartz oscillator and a divider which divides the outputs from the oscillator. To reduce power consumption of the oscillator, first, the examination has been made of the various circuit systems of the oscillator. However, all the above examination has been made on the circuit systems and the design constant for reducing the straight-through current which flows irrespective of oscillation. In the divider, the micronization of MOS structure and the examination on the circuit systems such as dynamic division has been made up to the present. The above conventional systems have been examined on the assumption that the employed battery voltage is used in the reference pulse generator as it is, taking an electronic timepiece for example. To reduce the power consumption, the drive voltage is reduced to satisfy the relation shown by the formula (1). EQU I=fCV (1)
where I denotes the power consumption, f the operating frequency, C the load capacitance and V the drive voltage.
Conventionally, a voltage V', which is lower than the drive voltage V, is used for an oscillating portion and a dividing portion of the reference pulse generator to reduce the drive voltage V.
FIG. 1 shows a conventional circuit structure comprising a power source 1, a reference voltage generator 2 connected with terminals 6 and 7 of the power source 1, a quartz oscillator 3 for producing an oscillatory output signal and being connected with a voltage generating terminal 9 of the reference voltage circuit 2 and a terminal 6 of a power source 1, a divider 4, the discriminator 5 for discriminating the start of oscillation of the oscillator in response to an output 11 from the divider 4.
FIG. 2 shows an example of a quartz oscillator, in which the following relation is generally held between the voltage V.sup.start necessary for starting oscillation and the voltage V.sup.stop necessary for maintaining the oscillation. EQU V.sup.start .gtoreq.V.sup.stop ( 2)
Thus, in the conventional method of reducing the power consumption by means of controlling the voltage, a voltage V.sub.D2 higher than V.sup.start and a voltage V.sub.D1 between V.sup.start and V.sup.stop are produced to drive the reference pulse generator at an optimum voltage for a long time. V.sub.D2 is applied to start the oscillation of the oscillator, and then V.sub.D1 is applied when the oscillator stabilizes in a normal oscillation state to drive the reference pulse generator. To change the voltage from V.sub.D1 to V.sub.D2 and vice versa, the discriminator 5, which discriminates whether the oscillator normally oscillates or stops, is needed. Since the oscillator changes going through several stages from the stop state to the normal oscillating state, and since the intermediate stages of the operating condition cannot be easily discriminated from an operating condition produced by an external noise, it is extremely difficult to drive the discriminator 5 precisely. For example, when the discriminator discriminates that the output 11 from the divider 4 produced by noise is normal, the output from the discriminator 5 controls the reference voltage generator 2 and changes the voltage V.sub.D2, which is necessary for oscillation to the voltage V.sub.D1, which does not start the oscillation but is sufficient to maintain the oscillation. As a result, the voltage is reduced although the oscillator does not oscillate normally, and it is impossible to then start oscillation. Thus, a precise discrimination of the discriminator is an absolute condition in case the closed loop is controlled, however, this method is extremely dangerous when applied to the reference pulse generator because the probability of mis-discrimination by the discriminator is high.